from turtle import *
from random import *
from math import *
def tree(n,l):
  pd()#下笔
  #阴影效果
  t = cos(radians(heading()+45))/8+0.25
  pencolor(t,t,t)
  pensize(n/3)
  forward(l)#画树枝
  if n>0:
    b = random()*15+10 #右分支偏转角度
    c = random()*15+10 #左分支偏转角度
    d = l*(random()*0.25+0.7) #下一个分支的长度
    #右转一定角度,画右分支
    right(b)
    tree(n-1,d)
    #左转一定角度，画左分支
    left(b+c)
    tree(n-1,d)
    #转回来
    right(c)
  else:
    #画叶子
    right(90)
    n=cos(radians(heading()-45))/4+0.5
    pencolor(n,n*0.8,n*0.8)
    circle(3)
    left(90)
    #添加0.3倍的飘落叶子
    if(random()>0.7):
      pu()
      #飘落
      t = heading()
      an = -40 +random()*40
      setheading(an)
      dis = int(800*random()*0.5 + 400*random()*0.3 + 200*random()*0.2)
      forward(dis)
      setheading(t)
      #画叶子
      pd()
      right(90)
      n = cos(radians(heading()-45))/4+0.5
      pencolor(n*0.5+0.5,0.4+n*0.4,0.4+n*0.4)
      circle(2)
      left(90)
      pu()
      #返回
      t=heading()
      setheading(an)
      backward(dis)
      setheading(t)
  pu()
  backward(l)#退回
bgcolor(0.5,0.5,0.5)#背景色
ht()#隐藏turtle
speed(0)#速度 1-10渐进，0 最快
tracer(0,0)
pu()#抬笔
backward(100)
left(90)#左转90度
pu()#抬笔
backward(300)#后退300
tree(12,100)#递归7层
done()